1. Field of the Invention
The invention relates to a method for producing a lens, in particular a spectacle lens, central aberrations of an eye, to be corrected, of an ametropic person, such as sphere, cylinder and axis, being compensated. The invention also relates to a lens that is produced using the method.
2. Description of the Related Art
Ametropias of eyes are generally corrected with the aid of spectacle lenses or contact lenses, in order to increase the visual acuity. For this purpose, the refracting values, such as sphere, cylinder and axis, of the spectacle lens or the contact lens that are optimum for raising visual acuity are determined in a subjective or objective measuring method. These data are then incorporated in a known way into a spectacle lens having two refracting surfaces, in which case the surface averted from the eye is generally a spherical surface and, given the presence of an astigmatism, the surface facing the eye is a toric surface rotated in front of the eye in accordance with the axial position.
Aberrations occurring in the case of a lateral view through a spectacle lens are reduced by using aspheric and atoric surfaces, aspheric and atoric surfaces constituting surfaces that deviate from a sphere or a torus, respectively. The use of such surfaces for reducing aberrations has already been practiced for a long time. Likewise known are irregularly shaped surfaces, so-called freeform surfaces, which are used, in particular in the case of progressive lenses, to achieve the rise in power in the near zone in order to support the accommodation. The production of such surfaces with the aid of CNC-controlled grinders, millers and polishing machines is likewise known from the prior art.
Furthermore, refractive measuring methods such as wavefront detection, are known that not only permit the values, already mentioned above, of sphere, cylinder and axis to be determined, but also aberrations of higher order over and above this. These aberrations are a function of the aperture of the eye pupil.
The size of the pupillary aperture is influenced, inter alia, by the brightness of the surroundings, medicaments, and the age and healthiness of the person being examined. In healthy adults, the pupillary aperture fluctuates between 2.0 mm and 7.0 mm. The pupillary aperture is smaller in daylight than in twilight or at night.
A refractive measuring method is known from EP 663 179 A1. The document describes a method with the aid of which refractive measurements can also be undertaken on an eye provided with a contact lens. Measurements are undertaken at different points of the contact lens/eye system. In a first step, a light beam is generated whose light source is selected from a group that comprises a plurality of point light sources and slit-shaped light sources. Thereafter, this light beam is guided directly into the eye onto the retina, and the light beam is reflected starting from there. The reflected light beam therefore strikes a scanning aperture. The passage of light through the scanning aperture is picked up by a camera, which generates an image signal. This signal is displayed on a monitor. The method and the device, as well, are of substantial use for measuring optical defects, deformations or aberrations of an eye.
Furthermore, DE 199 54 523 discloses a production method for contact lenses, the first step being to use a so-called wavefront detection method to determine the optical ametropia of an eye, and a soft contact lens being mounted on the cornea. The refractive measurement is carried out with the contact lens seated, a material removal method supported by laser radiation thereafter being applied on the contact lens separated from the eye. Owing to the removal of material supported by the laser, the contact lens assumes a surface shape by means of which a surface power that is determined by the optical correction data is obtained in the contact lens. Furthermore, information relating to the surface topology of the eye is obtained, and is likewise also incorporated into the correction.
U.S. Pat. No. 6,224,211 discloses a method that, in addition to the correction of the normal atropia, also permits a correction to the spherical aberration of the eye. Various aspheric contact lens that are designed for zero spherical and astigmatic action are mounted on the eye in each case. These lenses are used to determine how the spherical aberration of the eye can be corrected as best as possible. This information is used to determine an aspheric lens, which permits the optimal correction of the visual acuity and is matched to the patient.
Finally, DE 100 24 080 A1 discloses a method with which the complete correction of ametropias of the human eye is to be possible, a wavefront analysis device being used for this purpose. The substance of the aim here is a surgical correction of the eye itself. The dependence of the pupillary aperture on the aberrations of higher order is not taken into account.
The size of the pupillary aperture is 3.0 mm to 3.5 mm in daylight for healthy middle aged adults. With increasing age it decreases to approximately 2.0 mm to 2.5 mm. Since the size of the pupillary aperture can enlarge up to 7.0 mm as darkness grows, the effects of errors of higher order change as a consequence.